Heart Rate Training Zones

Most training plans are based on Intensity. Intensity is described by five training zones, Zone 1 to Zone 5. Many triathlon training plans divide the top zone in three: Zone 5a, 5b, and 5c. Athletes can use these zones to "tune" each workout for the best results.

The zones are set based on percentages of generally one of three values:

Lactate Threshold

VO2 Max

Maximum Heart Rate

Of these, Lactate Threshold has been shown to be one of the best predictors of endurance performance. Lactate threshold is the point at which your body can no longer get rid of the lactic acid produced by your muscles, and it starts to accumulate in the blood. This lactate threshold is closely correlated with heart rate and breathing rate.

VO2 Max represents the maximum amount of oxygen that can be used by the muscles during a specified period. Your base VO2 Max is genetically determined, but you can increase it by training. Maximum heart rate is, well, maximum heart rate.

Measuring lactate threshold require a medical test while on a treadmill or stationary bike. It can also be estimated based on very specific "field tests" on the bike or run. However, since there is the correlation to heart rate, which is easier to estimate, we most often talk about heart rate zones.

Note: Heart Rate Zone values are based on running. For each zone, subtract 10 beats per minute for biking and 10-15 beats per minute for swimming.

Used for: These are the easiest workouts, used to promote recovery after harder workouts. It is also generally the intensity level used during the recovery period of interval work and long slow distance (LSD) runs.

Used for: Intervals, hill work, and tempo work; typically used after some Zone 4 time has already been done. Zone 5 workouts are very short because it is difficult to maintain this level for any length of time.

Used for: Intervals and hill work to improve anaerobic endurance. Intervals in this zone generally have work-to-rest ratio of 1:1, for example, a 20 second sprint followed by 20 seconds of easy recovery (Zone 1).